One suggestion, the filing said, was that that Mateen may have actually conspired with his father, who was later put under investigation for wire transfers to Turkey and Afghanistan.

Investigators found receipts for the transfers — from March to June 2016 — when they searched Seddique Mateen's home after the June 12, 2016, massacre at Pulse, according to the email attached to a motion to dismiss filed Sunday.

Remembering the mass shooting at Pulse nightclub in Orlando

Seddique Mateen "has not been informed by the FBI about the investigation," Assistant U.S. Attorney Sara Sweeney wrote in the email.

Defendants weren't able to investigate "whether a tie existed between Seddique Mateen and his son, specifically whether Mateen's father was involved in or had foreknowledge of the Pulse attack," Scheller wrote in the filing.

The elder Mateen's ties to the feds suggest also he "played a significant role in the FBI's decision not to seek an indictment from the Justice Department for false statements to the FBI or obstruction of justice against Omar Mateen" during a 2013 probe into threats he made, the filing argued.

Salman's lawyers also argued the FBI went after her "based on its own motive to avoid responsibility for its failures with its own informant, Seddique Mateen, as well as his son."

Omar Mateen was under law enforcement investigation in 2013 until his father stepped in. (Myspace)

The suggestion that Seddique Mateen "may have been involved in the promotion of violent activities" complicated the case, Scheller argued, because he was a government witness. He was never called to testify.

Salman's lawyer also suggested Mateen's mother was misleading on the witness standing when she claimed to not be aware of any ties her husband had to the FBI.

Mateen killed 49 people at the Orlando night club in June 2016. (Joe Raedle/Getty Images)

Not providing the information violated Salman's so-called Brady rights, which require prosecutors to hand over any potentially favorable evidence.

"It is apparent from the Government's belated disclosure that Ms. Salman has been defending a case without a complete set of facts and evidence that the Government was required to disclose," the filing argues.